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in regards to a "double layer thingy...i made one... it was a super cheap alternative to an underquilt, that i made the night before a long cold winter backpacking trip. It was basically..... a bottom shell of nylon that i sewed little 1" pieces of velcro spaced around the edges. Then i took a cheap space blanket and reinforced areas with packing tape corresponding to the velcro on the shell, and put "sticky side velcro" on the reinforced areas. It made it so the space blanket was attached adequately to the shell, but removeable if i decided the VP was too annoying. Then i took an old sleeping bag and cut a 48"x26" chunk out of it... i then used 6 big safety pins to attach to the shell outer seam. I attached the shell via simple channels in the ends that i had elastic ribbon running through, which i just hooked onto the suspension of my hammock. There was a good amount of air between the sleeping bag and the shell/space blanket, like 3 inches. it did and excelent job of keeping me warm and the temps dropped down to 11 degrees F. with a light breeze.
Anyway, this system worked very well, but it was because of the space blanket being away from the sleeping bag. it weighed a TON! like 59oz, and i would have probly been fine in any of the high quality uq's out there....which weigh much less...

Originally Posted by DaleW

I rest my case

I am VERY pleased it works for you. But "works" and well designed can be very different things. Many manufacturers have done wonderful things with the main hammock bodies and the top quilts and tarps meld well. The integrated bug screens aren't bad, although some of the add-on ones are a little half-baked, but the insulation thing is just sad--- very, very sad. I think it can be done better.

I guess I'll have to learn to sew and show you guys how to get things done

like i have said when debating too much about what is the best way, or how to do it, or what problems will it have; when making many hammocking gear items...Just GRIP IT AND RIP IT!!! (not meant literally, dont rip your stuff up) But for a lot of things, you are not going to know what the issues are until it is made, and tested...grip it and rip it
-Dan

Even fools are thought wise if they keep silent, and discerning if they hold their tongues. Proverbs 17:28

For I consider that the sufferings of this present time are not worthy to be compared with the glory that is to be revealed to us....that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God. For we know that the whole creation groans and suffers the pains of childbirth together until now.
Romans 8:18,21-22

Gravity is not your friend...

Regardless of the type of fastener or how many you stick on the bottom of your hammock....gravity will win. Nylon stretches more than polyester, fabric stretches more than webbing, etc. If you attach a quilt with hard points it may work fine today then droop terribly tomorrow. A 150lb guy will freeze (because the hammock doesn't sag into the quilt) but the 300lb guy is fine.

Adjustability is the key with any underquilt system. You need it to be able to snug it up tight to keep your backside warm or allow it to droop for some ventilation. This is a problem our ground dwelling cousins will never have to face but a hard fact for hangers.

Shockcord isn't the most eloquent solution to this problem but it's light, cheap, and available. I know my quilt would fit much better if I went ahead and stitched some loops on the hammock edges and attached the cords there (rather than going to the ends). Matching points at each shoulder, the head, and around the knees on each side would certainly keep my quilt better in place.

Unfortunately.....I swap this quilt back and forth between my hammock and my son's. So I'd have to match this custom hanging setup on both rigs. Until I have the funds to build myself a custom insulated hammock for each season (like a hanging sleeping bag) I guess I'll just stick with the stuff I've got. I will try to improve upon it with lots of good ideas presented here on the forums.

In the "classic" sense, vapor barriers go between you and the insulation. In sub-zero conditions, your sleeping bag or quilt will gain weight and loose its insulating properties as your sweat freezes in the fill. Most use an inner bag liner for a barrier. In a perfect world, you don't give off much perspiration and what you do is kept warm by the nice *dry* insulation on the other side. Use a closed vapor barrier at 50F and you'll be a mess. At -20F, you will probably be warmer and your insulation will stay dry.

Putting the space blanket under your insulation helped to cut wind and convection losses. You may have gotten some heat reflected back towards you-- not much at that distance, but better than none

Space blankets work well to cut wind and rain. It will reflect heat and best if it isn't quite touching you. Hanging a space blanket *just* below your hammock bottom will product the best results. If you have space blankets on both sides of your insulation, then you get the reflection, the vapor barrier, and the wind barrier.

Condensation accumulating somewhere between the top of the space blanket and the user is an issue. That depends on dew point/humidity, the breathability of the hammock fabric, layers between you and the hammock (compressed sleeping bag and clothing), and ventilation (air leaks). I don't have a complete grasp of how the difference in temperature really effects it all with a hammock-- what happens at 40F vs. -20F and back to the dew point stuff. For my use, I am more concerned with lightweight systems down to 32F and high humidity.

Insulation is all about creating a dead air space between your warm body and the cold cruel world outside. Just dead air doesn't work, as you get convection currents going inside the aid space, transferring the heat to the cold outer cover. That is why plain air mattresses are cold. So we add filler to stop the air from moving--- the fiberglass batts in your walls and ceiling, or the insulation added to air mattresses, or CCF pads with lots of little bubbles and a material that doesn't transmit heat well, or feathers or fluffy fibers. Down is all about light weight and compressibility-- it maintains a large *still* air space, it is light for the loft it produces, and can be compressed for travel. You have to keep down dry, so the system needs to be ventilated.

Always remember that there is no such thing of force as "cold," only more or less heat. The battle is keeping the heat that you make in your body. You aren't keeping the cold out, you are trying to stop the heat in your body being transferred to the cold air or ground.

Hmmm. A lot of people are putting a lot of thought into the question of bottom insulation. That bodes well for future solutions, but it also says a lot about the state of the art - there's a lot of room for improvement. By the way, I'm working on a few things, too...

Hmmm. A lot of people are putting a lot of thought into the question of bottom insulation. That bodes well for future solutions, but it also says a lot about the state of the art - there's a lot of room for improvement. By the way, I'm working on a few things, too...

A hot water system with a circulating pump would be so warm Like a radiant floor.

Regardless of the type of fastener or how many you stick on the bottom of your hammock....gravity will win. Nylon stretches more than polyester, fabric stretches more than webbing, etc. If you attach a quilt with hard points it may work fine today then droop terribly tomorrow. A 150lb guy will freeze (because the hammock doesn't sag into the quilt) but the 300lb guy is fine.

You're thinking open-ended underquilts. I'm thinking undercovers with insulation inside. And I have to admit, anything I make will have synthetic fill, and everything is pretty well battened down. I am thinking full or at least 3/4 coverage too.

With an undercover and the quilt attached to the bottom of the hammock on all four sides, there is no droop. If you must, the insulation can easily have drawstrings in the ends, but with Velcro fastening to the hammock bottom, I don't know where it can go.

If there is a weak point in fastening the UQ to the hammock, it is at the top edge near your left shoulder and right of your feet, where there will be a couple inches of stress on top of the insulation, which may compress it a bit. Your top quilt should be doing the job, but if not, maybe it needs a little foam or Insultex "bumper" in those areas. The outer cover should be good 'n loose in those areas too.

And you don't have open air gaps with the under cover. There is no opportunity for moving air to get to the middle/bottom where things tend to sag. You have one more layer in play vs an add-on UQ if you are putting quilted down insulators in there.

You're thinking open-ended underquilts. I'm thinking undercovers with insulation inside. And I have to admit, anything I make will have synthetic fill, and everything is pretty well battened down. I am thinking full or at least 3/4 coverage too.

With an undercover and the quilt attached to the bottom of the hammock on all four sides, there is no droop. If you must, the insulation can easily have drawstrings in the ends, but with Velcro fastening to the hammock bottom, I don't know where it can go.

If there is a weak point in fastening the UQ to the hammock, it is at the top edge near your left shoulder and right of your feet, where there will be a couple inches of stress on top of the insulation, which may compress it a bit. Your top quilt should be doing the job, but if not, maybe it needs a little foam or Insultex "bumper" in those areas. The outer cover should be good 'n loose in those areas too.

And you don't have open air gaps with the under cover. There is no opportunity for moving air to get to the middle/bottom where things tend to sag. You have one more layer in play vs an add-on UQ if you are putting quilted down insulators in there.

As was mentioned earlier, Speer Hammocks sold an UQ that would attach to a Speer hammock with the velcro also used to attach the bugnet.

It was an excellent design, but it never caught on with enough popularity to remain in production after Speer's merger. The differential cut allowed it to overcome issues with compression in relation to fit.

Thanks for the info and photo! I like it-- very simple and easy to deploy (and clone). I built a model last night, with an idea to sewing the under cover in place, but I am leaning to Velcro, especially for prototyping. I'm still thinking about baggy box-shaped under cover that covers all but the last foot or so of each end. Kind of like taking the Clark pockets idea and replacing them all with one continuous compartment. I'm thinking very seriously of adding Velcro to my Hennessy Zip and making insulation modules for that, borrowing from the Garlington Insulator concept. With Velcro it would be easy to ventilate the pocket too.

Differential cuts are mandatory to avoid compressing the insulation. With the Speer version, the issue with air gaps is eliminated all the way around and it does leave the opportunity for different quilts to be mounted. It would be easy to make a partial quilt with light fabric ends or just a lighter quilt overall. You could insert a vapor barrier/space blanket, Insultex liner, and so-on. Some have written that the UQ needs to be tight against the user, but I think that is more an issue with air gaps on a shock-cord mounted UQ, where you get gaps on the ends and air leaks down the unfixed sides.

The idea for a Velcro bug screen had occurred to me. I would have Velcro on the outside of the underquilt, so you could attach the screen to the quilt, or to the hammock body without the quilt in hot weather.

You're thinking open-ended underquilts. I'm thinking undercovers with insulation inside. And I have to admit, anything I make will have synthetic fill, and everything is pretty well battened down. I am thinking full or at least 3/4 coverage too.

With an undercover and the quilt attached to the bottom of the hammock on all four sides, there is no droop. If you must, the insulation can easily have drawstrings in the ends, but with Velcro fastening to the hammock bottom, I don't know where it can go.

If there is a weak point in fastening the UQ to the hammock, it is at the top edge near your left shoulder and right of your feet, where there will be a couple inches of stress on top of the insulation, which may compress it a bit. Your top quilt should be doing the job, but if not, maybe it needs a little foam or Insultex "bumper" in those areas. The outer cover should be good 'n loose in those areas too.

And you don't have open air gaps with the under cover. There is no opportunity for moving air to get to the middle/bottom where things tend to sag. You have one more layer in play vs an add-on UQ if you are putting quilted down insulators in there.

If the insulation's weight manages to push the UC downward more than the insulations ability to loft up and fill the space between the UC and hammock, there might be a problem. And more so if the UC is not very well sealed at all edges and the end, leaving an open path for cold air to flow downward and fill that even very small gap between your back and the insulation. Both the distance between the weighted ( with insulation) UC- after laying in the hammock- and the amount/loft of the added insulation will have either be just right- or adjustable. Obviously can be done with Velcro or snaps, but it will need to be pretty custom.

A Speer PeaPod- when fully or mostly closed- is supported by the nylon cords that tie it to the ends of the hammock, AND by the top side Velcro closure along the entire length. I adjust mine so that either, once I lay down, the bottom inside is barely in contact with my back, or if I want to add a jacket something for more loft, it has an inch or 3 gap after I lay down, but before adding extra insulation. ( or an unfilled gap if it is kind of warm out) That means I either start out with a 4-6" gap between the pod and un-occupied hammock, or more if I plan on adding something. if after I am in, I see that it is either too tight (compressing loft) or to loose with too much gap, I just get out and make one small adjustment on one end. Mostly, I never even have to do this. Once all of this is done, it will stay put due to the non-elastic end cords and the full length Velcro closure, pretty much ending any worries of any thru the night sag. Also, as it is cinched tight around the hammock on the ends, and closed as tightly as desired along the top, with thick loft draping over the hammock edges and down onto the user, there really won't be any cold air rushing in to fill any unintended gap under your back.

True it is added on, but it sure has been bomb proof, on more than one brand of hammock, for me. I just has not failed me up to 10F below it's rated temps, with addition of either puffy clothing or a 40-50F TQ and a space blanket below.

The insulated hammocks are interesting concepts, though they have all been DIY. That will save the weight of one layer of nylon. Just a larger layer of nylon sewn to the hammock and filled with insulating material. But venting in warm weather MIGHT be a problem, I suppose?

For I consider that the sufferings of this present time are not worthy to be compared with the glory that is to be revealed to us....that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God. For we know that the whole creation groans and suffers the pains of childbirth together until now.
Romans 8:18,21-22